Added damage editing and potion editing

Potion Editing

Usage

/potionedit <add|remove|color|clear> [arguments]

Arguments

add <effect> [duration] [amplifier]: Adds specified effect with specified duration and amplifier to potion's effects remove <effect>: Removes effects of specified type from potion (only works for custom-added effects) clear: Clears all custom-added effects from item

Damage Editing

Usage

/itemedit damage <damage>: Sets the damage value for item to specified value